Latinos, the fastest growing segment of the US population, carry disproportionate rates of chronic illnesses such as obesity and diabetes and have the highest levels of physical inactivity Among Latino subgroups;Mexican American women experience some of the highest rates of obesity and sedentary lifestyles. Increasing daily moderate-intensity physical activity (PA) can prevent weight gain and improve overall physical and mental health. The aims are to: 1) identify and understand the factors that influence PA behavior for Mexican immigrant women in the Columbia MSA, SC;2) develop and evaluate a culturally competent PA intervention that targets individual, family and community influences among Mexican immigrant women;and, 3) assess the feasibility and effectiveness of engaging community-based Lay health advisors (LHAs) as participatory researchers. In year 1 we propose to conduct formative assessments and develop the intervention in full partnership with a local Hispanic-serving organization and other community partners via a Program Advisory Team. Six LHAs will be recruited to participate in the planning and implementing the formative assessments. Data gathered from 12 focus groups and 25 in-depth interviews will inform the development of an intervention to promote moderate intensity PA among Mexican immigrant women. In year 2, each LHA will recruit 2 groups of 10 women (N=12 groups;N=120 women) to participate in the study. Each group will be randomly assigned to one of two conditions: an immediate intervention or a delayed intervention. Randomization will be balanced within LHA. Six groups will receive the immediate intervention and 6 groups will be measured as part of the delayed intervention. At the conclusion of the 6- month intervention, delayed intervention groups will receive the intervention (but no measurements). The intervention, based on Social Cognitive Theory and PEN-3 and Socio- ecological models, will be delivered by LHAs and emphasize meeting CDC-ACSM recommendations of 30 minutes of moderate-intensity PA on 5 or more days per week. Thus, in addition to individual behavior change, the intervention will target the social and cultural influences within the Latino family and community. Standardized assessments will occur at baseline and 6-months follow-up and PA will be assessed using accelerometers. We hypothesize that compared to participants randomized to the delayed intervention, immediate intervention participants will show greater increases in minutes per day moderate intensity physical activity (primary outcome), show greater increases in perceived social support and self- efficacy for physical activity and less weight gain (secondary outcomes). PUBLIC HEALTH RELEVANCE This proposal will lay the foundation for rigorous evaluation of the incorporation of lay health advisors in a participatory research approach to affecting physical activity among Mexican immigrant women. The study will provide preliminary evidence for the feasibility of this approach, including logistical issues, levels of community participation, potential effect sizes for behavioral outcomes, and the cultural suitability and reliability of measures. These preliminary findings will be used to develop a large-scale, community-based trial of the participatory, lay health advisor approach to promoting physical activity in Latino communities and assisting in the reduction of health disparities.